Advances in building requirements and technologies emphasizing energy conservation have resulted in insulated and sealed buildings. As a result, moisture related structural integrity and the indoor air quality (IAQ) management of these types of buildings have become a major concern. In recent years, considerable effort has been made to improve the performance of building envelopes. While this effort has brought about considerable improvements in building performance, water related problems still persist.
What is crucial is having knowledge of the severity and extent of any water intrusion. A critical parameter is the ability of the building materials to store and then disperse excess moisture. When not overwhelmed, buildings can absorb and manage a quantity of moisture. It is only when moisture levels accumulate to a critical level over a measured period of time that issues causing moisture related mould and damage arise.
Early detection and location of building envelope penetration will allow a builder or owner to identify developing problems and to carry out minor repairs. Homeowners, builders, and insurance companies can avoid high costs that are incurred from extensive structural damage, health problems, insurance claims and potential litigation.
Water can collect in a building envelope as a result of infiltration or exfiltration and condensation. Rain storms and condensation can result in small amounts of water leaking into a limited number of locations in the wall and roof assemblies. The building is able to absorb and eliminate limited amounts of moisture. This wetting and drying process is within the normal performance parameters of the building enclosure and should not result in a threshold alarm. Warning of excess moisture levels should be issued only when moisture accumulates and grows in area over an extended period of time.
In assessing the moisture performance of a building envelope several important variables must be measured, assessed and combined to derive an estimate of the risk and corrective action needed. Key parameters include moisture level, duration of moisture event, number of simultaneous events and surface area involved.
Several moisture monitoring systems are described in the literature but all share the common limitation of setting a moisture alarm threshold and a relatively small number of monitored points. This can lead to misinterpretation of the building envelope performance and result in unnecessary and costly opening and repair of otherwise well performing wall and roof assemblies.
There are several types of moisture detection sensors available for detecting water leaks.
In U.S. Pat. No. 6,175,310 (Gott) issued Jan. 16, 2001 there is disclosed an arrangement which uses exposed conductors on a tape of a hygroscopic material where the current across the conductors is detected to detect moisture enveloping the tape.
In U.S. Pat. No. 6,377,181 (Kroll) issued Apr. 23, 2002 there is disclosed an arrangement which uses probes which are each connected to a conductor pair communicating with a central monitor which issues an alarm when moisture above a threshold is detected.
In U.S. Pat. No. 6,144,209 (Raymond) issued Nov. 7, 2000 there is provided an arrangement which describes a location method using a combination of specially designed insulated and detection conductors cabled together in a form helix. This design while useful for detection and location of water on floor like surfaces can not be placed between the roof deck and waterproof membrane because of the large overall dimensions and the susceptibility of the cable design to crushing and shorting.
U.S. Pat. No. 4,502,044 (Farris) issued Feb. 26, 1985 discloses a plurality of sensor elements defined by side by side pairs of conductors which are adapted to be mounted in two walls of a building and which connect to a central control unit. The control unit uses a transistor which acts to detect when voltage across a resistor reaches a value sufficient to turn on the transistor to emit an alarm signal.
British Patent Application 2,235,535 (Stewart) published 1991 discloses a plurality of sensor elements defined by tapes 3 which are mounted in walls of a building and connect to a central control unit in the form of a leak detection
U.S. Pat. No. 5,081,422 (Shih) issued Jan. 14, 1992 discloses in general a plurality of moisture sensor elements each defined by a side by side pairs of conductors which have a resistance characteristic which varies in relation to a moisture content. Shih also discloses the use of probes which are connected to the wires and are driven into the material on which the wires are attached.
The present Applicants also disclose arrangements in Published PCT Application WO/05/10837 published Feb. 3, 2005. These arrangements use detection tapes and probes are suited for detecting water intrusion in selected areas of a building structure. The disclosure of the above application of the present Applicant are incorporated herein by reference or may be reviewed for further details not disclosed herein.
Also in U.S. application Ser. No. 11/229,312 filed Sep. 19, 2005 entitled “A MOISTURE DETECTION SENSOR TAPE WITH LEAK LOCATE”, which corresponds to Canadian application Serial No: 2,520,202 filed Sep. 19, 2005, is disclosed an improved tape using four conductors which allow a location process to be used to locate the position of the leak along the tape. The disclosure of the above application of the present Applicant are incorporated herein by reference or may be reviewed for further details not disclosed herein.
Also in U.S. application Ser. No. 11/679,673, filed Feb. 27, 2007, “A MOISTURE DETECTION SENSOR TAPE AND PROBES TO DETERMINE SURFACE MOISTURE AND MATERIAL MOISTURE LEVELS”, which corresponds to Canadian application Serial No: 2,583,006 is disclosed a moisture detection sensor is used in a building structure to detect moisture penetration. The sensor is a flat adhesive tape of a substrate of dielectric, hydrophobic material. Three or four elongate, parallel, conductors are secured to the top surface and a protective layer of non-hygroscopic, water pervious material is secured over two of the conductors so that they are exposed to surface moisture. One or two of the conductors are covered by an insulating layer to prevent moisture access. Pairs of moisture probes along the length of the tape penetrate the insulating layer, the respective conductors and the substrate and to extend into a building component to which the substrate has been adhered. A diode guide arrangement allows a monitoring unit to monitor the exposed conductors for surface moisture and the penetrated conductors for moisture in the component by reversing polarity of the voltage across the conductors. The disclosure of the above application of the present applicant are incorporated herein by reference or may be reviewed for further details not disclosed herein.
In published US Patent Application 2006/0092031A1 published May 4, 2006 and entitled Building Monitoring System by Vokey is disclosed a building monitoring system which monitors selected zones in a building structure for the presence of moisture. The system uses multiple moisture detectors each installed in the structure at a location to be monitored. A remote sensor unit is associated with each zone to be monitored and is coupled to the detectors in the associated zone. The sensor unit generates an alarm signal having a characteristic uniquely representing the sensor unit and any wet detector to pinpoint any leakage problem. A monitoring unit receives alarm signals from the sensor units, decodes the alarm signals and generates an alarm report reporting the existence and location of any leakage.